(A) Field of the Invention
The invention relates generally to Physiological display systems and more particularly to CRT storage tube devices that are utilized to display electrocardiographic signals which have been processed and categorized by computer analysis into normal and abnormal beats. The electrocardiographic signals (ECG) result from electrical currents that circulate upon the skin surface as a result of the expansions and contraction of the cardiac muscle (heart). The ECG signals are useful to the clinical physician since certain known and identifiable abnormalities are known to produce particular waveform irregularities. These irregularities however, may occur infrequently, or intermittently, and their occurence may depend upon the patients' stress or activity. It is thus desirable to accumulate large volumns of continuous data during times when the patient is engaged in carrying out his normal day to day activities. For this purpose, a small compact tape recorder is worn by the patient as he performs his usual functions. The recorded tape can be taken to a laboratory and rapidly replayed analyzed, and formatted for display. During the analysis, abnormal beats may be categorized and marked for identification.
(B) Description of the Prior Art
The expansion and contraction of the cardiac muscle produces surface skin electrical signals which can be recorded and analyzed to determine the condition of the heart. Of interest to the physician is an analysis of continuously recorded signals over an extended period particularly during the normal day to day activities of the patient. Known types of anomalous signals that represent arrhythmic (irregular variations in rhythm) and ectopic (ventricular ectopic and superventricular beats) activity can then be identified and treatment prescribed.
The analysis is accomplished by recording the ECG signals in real time on a small compact tape recorder which is worn by the patient as he carries out his daily activities. The recorded ECG signals are then processed by replaying the signals on a cathode-ray oscilloscope. One particular type of prior art replay in fast time utilizes the superposition of predecessor complexes and is known as an AVSEP.RTM. display. An example of a system which may be used for the recording and playback of ECG signals with the recording in real time and with the playback in fast time, reference is made to U.S. Pat. No. 3,215,136, issued Nov. 2, 1965 in the name of Norman J. Holter, et. al.
An extension of the prior art ECG scanning device described above, an improvement as shown in U.S. Pat. No. 3,718,772, issued on Feb. 27, 1973 in the name of Clifford Sanctuary, discloses a display system wherein recording is carried out at a very slow speed on a single tract with subsequent playback at a high speed so as to visually superpose a plurity of waveforms on an oscilloscope. A further extension of the prior art is shown in U.S. Pat. No. 4,006,737 filed Jan. 4, 1974 by Issac Raymond Cherry for a scanning device for the processing and presentation of simultaneous ECG data from at least two pairs of leads located in different positions on the patient.
Of particular interest with respect to the present invention is U.S. patent application, Ser. No. 356,326 by Alan S. Wong, filed Mar. 10, 1982, entitled, "An Improved Method and Apparatus for Displaying Electro-Cardiographic Signals" and U.S. patent application No. 06/510,677 by Alan S. Wong, filed July 5, 1983 entitled "Physiological Display System", both of which are hereby cross referenced to this application, the contents of which are referred to as background information relative to and for the purpose of understanding the present disclosure. In both of these applications, the physiological waveform is traced on a CRT storage tube, along with the time of day and patient information. Ser. No. 356,326 teaches how the display is marked to identify those physiological events which have been detected by the system as being abnormal. By tracing the first-channel during a first-sweep while storing the second-channel within a memory for use during the second-sweep, two independent channels of physiological data may be displayed on alternate rows. Various display formats may be selected by the operator, the operational modes being determined by command signals operable coupled to program counters which sequentially step through various memories devoted to the storage of the digitized physiological signals to be converted to analog for display. In Ser. No. 356,326, the display format is typically a two dimensional array comprised of successive lines of continuous waveforms as measured in time, beginning at the top of the CRT storage tube and proceeding from left to right and from top to bottom in time. After completion, ectopic events are recognized and corrolated with their time of occurence, and a subsequent sweep is generated so as to place small markers adjacent to those abnormalities which are identifiable as constituting at predetermined deviation from the norm. It will be understood that it is desirable to minimize the size of the markers to avoid cluttering, particularly where a large amount of real time data is to be played on a single frame. It will also be evident however, that small markers are difficult to observe. What is actually desired is a system for emphasizing small markers so that they can be easily identified.
Accordingly, a primary object of the invention is to provide a physiological display system wherein abnormal events are identified by markers having a visual characteristic which distinguishes the markers from the displayed physiological data.
A further object of the invention is to provide an apparatus which periodically refreshes selected aspects of a storage tube display.
A further object of the invention is to provide refresh signals to cause selected portions of a storage tube display to "blink" in accordance with the refresh signal rate.
Other objects and advantages of the present invention will be obvious from the detailed description of a preferred embodiment given herein below: